Avoid using Random instance by multiple threads. Although it is safe to share this instance, competition on the same seed will damage performance. Note: Random instance includes instances of java.util.Random and Math.random().
Examples:
<pre>
    Positive example 1：
    /**
     * @author caikang
     * @date 2017/04/07
     */
    public class RandomInThread extends Thread {
        private Random random = new Random();
        @Override
        public void run() {
            long t = random.nextLong();
        }
    }
    Positive example 2：
    /**
     * @author caikang
     * @date 2017/04/07
     */
    public class RandomInThread extends Thread {
        private Random random = ThreadLocalRandom.current();
        @Override
        public void run() {
            long t = random.nextLong();
        }
    }
</pre>